1. Field of the Invention
This invention pertains generally to the field of aircraft display units that present flight information to the pilot or flight crew of an aircraft.
2. Description of the Related Art
In present-day aircraft operations, whenever a flight management system (“FMS”) is an active source of navigation information, pilots have the ability to integrate information from several sources in order to understand how the aircraft is operating now and how it will operating next. For example, a primary flight display (“PFD”) could display current lateral, vertical, and speed/thrust flight modes, armed lateral and vertical flight modes, an FMS flight plan target altitude, and an FMS target airspeed. An FMS route window or “legs” page could display cumulative or leg distance to each waypoint, time to each waypoint, altitude and speed constraints at each waypoint (if any exists), and an FMS calculated altitude at each waypoint. A vertical situation display could display any existing altitude constraints, a top of climb (“TOC”) indication, and a top of descent (“TOD”) indication.
Even if the pilot is successful in scanning and integrating all of the above information presented in different locations in the cockpit, he or she may not know exactly when the aircraft will perform its next maneuver. For example, turn anticipation of a fly-by the waypoint will commence prior to the aircraft actually reaching the waypoint. Also contributing to the pilots' workload in comprehending the aircraft's current and future states is a proliferation of Vertical Navigation (“VNAV”) sub-modes. In addition to “getting behind the aircraft,” the inability of the pilot to maintain situational awareness of what the FMS is doing may lead to pilot to ask the classic question, “Why did the aircraft do that?”
Generally, the issue is not “what” the aircraft did, for a pilot may infer an answer from the sources of information discussed above. Instead, the issue may be “why” the aircraft did something at a certain point in time, thereby indicating a possible loss of temporal awareness of upcoming route and/or flight mode changes on the part of the pilot.